The invention relates to a dispenser or a metering apparatus, respectively, for precisely supplying fluid media out of a storage vessel to a receiver.
Such dispensers are used for precisely metering or dosing, respectively, fluid media as well as for titrating purposes. Said apparatuses can be used for metering greater volumes, such as liters, as well as for metering small volumes, such as microliters.
There exist already metering apparatuses comprising a metering piston pump having a glass cylinder. Said cylinder exhibits a graduation from which readings can be taken showing the volume of fluid medium taken out from the storage vessel. Normally a flask is used as such a storage vessel.
Metering apparatuses of the kind in re serve mainly the purpose of discharging or supplying, respectively, several times a constant and predetermined quantity of liquid. In order to achieve this goal the piston stroke and consequently the volume supplied during each metering action is adjusted to a certain height or amount, respectively. This is achieved for instance by providing for a length of stroke with the help of two stops, i.e. a fixed stop and an adjustable stop. By adjusting the adjustable stop also the stroke of the piston is limited and adjusted thereby.
Such a metering apparatus (also called batching device) is for instance described in the European patent application EU-A- 831 01699. The adjustable stop of this known metering apparatus can be rotated in the peripheral direction of said device in order to change the length of stroke. The counter stop consists of a stepped gauge. By rotating the adjustable stop the length of stroke can be changed.
Since a stepped gauge is used the length of stroke can be changed and adjusted in great steps only.
There are known furthermore metering apparatuses comprising an adjustable length of stroke, for instance from the German Laid-open Print DE-A- 35 34 550. The dispensed amount of fluid to be discharged or sucked in, respectively, is determined with a contact-free scanning measuring system.
The metering piston pump, the stop means, if present, for limiting the length of stroke of the piston as well as the measuring system, if present, of said known dispensing devices or measuring apparatuses, respectively, are either contained in a housing or made up in such a way that some of the elements mentioned are situated out of the housing of said apparatuses. Therefore, said known metering apparatuses are difficult to clean and are not designed in an ergonomical manner.
The underlying aim of the present invention is to provide a dispenser or a metering apparatus, respectively, of the kind in re the length of stroke of which (and therefore the stroke volume of the amount of liquid to be discharged) can be adjusted in a simple but very exact manner.
A further aim of the present invention is to provide a dispenser which can be used in a simple and effective manner.
These aims are achieved according to the present invention by a dispenser for precisely supplying fluid media from a storage vessel to a receiver comprising a cylinder being mounted in a fluid tight manner in a valve chamber which can be connected with the storage vessel and which contains a suction valve and a discharge valve; a piston which is slidably guided in the cylinder and which is connected integrally in rotation at its end opposite to the valve chamber (2) with an operating button; an adjustable stop for changing the length of stroke of the piston and a counter stop cooperating with the adjustable stop; said operating button being tightly fixed to an axially movable and rotatable threaded bush which is concentrically arranged with respect to the cylinder and runs around outside thereof, whereby the operating button is freely rotatable with respect to the threaded bush but can be connected integrally in rotation via a connecting element with said threaded bush which is equipped on its outer casing with an external thread, whereby said adjustable stop is a stop nut integrally in rotation and concentrically with respect to the threaded bush and where said stop nut is equipped at the inner casing of its inner bore hole with an inner thread cooperating with the outer thread of the threaded bush such that said stop nut is axially displaced if the threaded bush is rotated.
Consequently, the cylinder of the dispenser of the present invention is mounted in a fluid-tight manner in a valve chamber or valve block, respectively, which is known per se and which contains a suction valve and a discharge valve.
A piston is slidably guided in said cylinder. The piston is, after being introduced into the cylinder, longer than the cylinder and is connected integrally in rotation at its free end with the operation button. For cleaning purposes the piston can be taken out of the cylinder.
Said operating button is connected with a rotatable and axially movable threaded bush which is arranged concentrically with respect to the cylinder and encompasses the latter. The connection is such that the operating button can be freely rotated with respect to the threaded bush, but is fixed in axial direction. The operating button can be connected via a connecting element frictionally and therefore integrally in rotation to the threaded bush. Said connection integrally in rotation is, however, detachable.
The threaded bush extends preferably over the complete height of the cylinder. Preferably it extends beyond the cylinder and has the form of an extension being described later. The threaded bush is equipped on its outer casing with an outer flat which extends preferably about almost the complete height of the threaded bush.
The adjustable stop of the dispenser of the present invention is a stop nut which is arranged concentrally with respect to the threaded bush and which encircles the latter. The axial height of the stop nut makes out for instance 1/10 to 1/3 of the length of that region of the cylinder which extends beyond the valve chamber. The stop nut is equipped at the inner casing of its inner bore hole with an inner thread which cooperates with the outer thread on the threaded bush. Said stop nut is guided integrally in rotation and therefore does not rotate.
By rotating the threaded bush with the operating button which can be connected integrally in rotation therewith via a connecting element the stop nut is displaced in axial direction.
The stop nut is preferably with the complete inner surface of the inner bore hole in contact with the threaded bush so that no tilting of the system can take place when the stop nut is moved.
By upward repulling the operation button also the threaded bush and together therewith the stop nut is moved upwards and so far until the stop nut comes in contact with a counter stop which is mounted at the upper end of the dispenser of the present invention. The length of stroke is adjusted by the position of the stop nut with respect to the threaded bush. The further down the stop nut is located at the threaded bush, the greater the stroke is (and therefore also the volume of the liquid to be dispensed which is sucked in by the piston).
The outer thread of the thread bush is preferably a multiple thread in order to be able to exactly adjust the height of the stop nut with respect to the thread bush. Said thread can be a round thread or a tapered thread.
The thread is preferably made up in such a way that five rotations are sufficient in order to move the stop nut from its lower position to the upper position.
The frictional connection which is therefore integrally in rotation between the operating button which is normally free rotatable with respect to the threaded bush and the threaded bush is achieved by a connecting element which can be pressed on from the outside.
The guidance integrally in rotation of the stop nut can be a common guidance, for instance a projection which is guided in an axially extending groove or slot.
According to a preferred embodiment the dispenser of the present invention is equipped with a measuring system which indicates the present position of the stop nut. Preferably a measuring system is used which produces electronic impulses upon movement of the piston (this means that also the threaded bush and the stop nut is moved). Said measuring system also registers and processes said impulses. Said measuring system can be an analogue measuring system, for instance a capacitive measuring system. Preferably a digital measuring system which displays after evaluation in an evaluation circuit the determined result on a digital display unit is used.
The measuring system comprises preferably a glass scale stick which is equipped with a glass scale. Said glass scale stick is arranged parallel to the cylinder and the threaded bush and sidewards therefrom. Said stick extends through an opening in the stop nut. Said opening is preferably provided in an extension at the side of the stop nut. By said means it is ascertained that the stop nut cannot rotate. The glass scale is scanned by a sensor head as described later down.
The measuring system is preferably controlled by a microprocessor which makes it possible to calibrate the volume dispensed by an analytical balance. This makes it furthermore possible to apply a correction factor to the number of measured impulses and to thereby assign said number of measured impulses to the volume which has indeed been dispensed. Thereby it is assured that all mechanical deviations of the diameter of the piston and the cylinder are limited and therefore taken care of.
Said measuring system together with the possibility of mechanically adjusting the stop means make possible that the stop is adjusted in an indefinite variable and exact manner. Consequently the volume dispensed can be exactly defined.
Due to the fact that the glass scale stick extends through the above described opening in the stop nut said glass scale stick of the measuring system assures at the same time that the stop nut is not rotated when the thread bush is rotated. Said stop nut is rather held integrally in rotation.
In an ergonomically designed and easy to be used embodiment of the dispenser of the present invention the cylinder and the piston (they form together a metering piston pump), the stop means together with its parts and the measuring system are contained in a perpendicular housing having an at least approximately cylindrical shape.
The valve chamber is known per se and contains a suction valve and a discharge valve. Said valve chamber is located in the lower region of the housing and can be put on the storage vessel or can be screwed on said vessel.
The cylinder, the piston which can be displaced within said cylinder, the stop means comprising for instance the stop nut, the threaded bush and the counter-stop as well as the measuring system are located above the valve chamber in that region which extends axially upwards from said valve chamber.
The free end of the piston is connected integrally in rotation with an operating button forming the upper end of the dispenser of the present invention.
The functional parts or elements, respectively, which make possible that a certain and predetermined volume is dispensed and the part for limiting the stroke length of the piston as well as the elements for registering or measuring, respectively, the height of the piston and therefore the stroke volume form together a functional group which is located in the perpendicular cylindrical housing (hollow cylindrical casing).
The operating elements, the display unit, for instance a LED- or LCD-display, the power source and the discharge pipe are located in an extension at the side of the abovedescribed housing. Said extension can be for instance a sprout-like arm. According to a preferred embodiment said sprout arm has the shape of a flat and lying block of stone the longitudinal axis of which is slightly inclined downwards with respect to the horizontal line. The expression "lying" makes clear that one of the great side walls of the block of stone form the lower boundary of the sprout-like arm. The other side wall of the two great side walls of said block of stone forms the upper boundary.
The discharge pipe extends through the free end of the sprout-like arm and therefore through one of the front faces of the block of stone and projects therefrom. At the free end the discharge pipe is inclined downwards and is therefore arranged in a vertical manner. The region of said discharge pipe which is found outside of the sprout-like arm is preferably supported by a rigid protecting sleeve which can be made for instance out of suitable plastic or out of steel. The discharge pipe is thereby supported and stabilized so that splashing of the dispensed liquid at the end of the discharge pipe is avoided.
The display unit and the operating elements are located in the upper region of the sprout-like arm. Due to this ergonomical arrangement they can be easily observed and manipulated, for instance by an upright standing person.
The housing is preferably composed of segments which can be put together. The lower segment surrounds the valve chamber, extends on the side which faces away from the sprout-like arm up to the lower region of the cylinder and surrounds also the lower region of the sprout-like arm and of the protecting sleeve of the discharge pipe.
The upper segment is the upper part of the hollow cylinder of the housing and surrounds the upper regions of the cylinder and of the threaded bush and surrounds also the connecting element for the operating button as well as for the threaded bush.
In the side wall of said upper segment facing towards the sprout-like arm an opening is found in which the operating knob is located. By pressing on said operating knob the connecting element is pressed in a frictional manner against the operating button (in particular against a flange extending downwards from the upper region of the operating button) as well as against the upper end of the threaded bush.
The third segment of the housing forms the upper cover wall of the sprout-like arm having the form of a block of stone and extends from the lower end of the upper segment up to the end of the sprout-like arm and also beyond said arm so that the third segment forms also a part of the protecting sleeve for the discharge pipe. Said third segment exhibits several openings in which a display or display unit, respectively, and operating buttons are put.